Microfluidic device and a method for preparing the microfluidic device from a photosensitive element

Abstract

A microfluidic device is formed from a cover member and a microfluidic precursor that is prepared from a photosensitive element. The photosensitive element is a solid layer of a photopolymerizable composition that includes at least a binder, a monomer, and a photoinitiator. A method for forming the microfluidic device from the photosensitive element includes imagewise exposing the photopolymerizable layer to actinic radiation through a mask and treating to form a relief surface having microstructures or features, such as one or more channels and one or more chambers, that are suitable for use in the microfluidic device. The method provides microstructures that can be formed to have different dimensions that provide particular advantages for a microfluidic device that is operated by degas-driven flow to transport a fluid through the microstructures.

I claim: 
     
         1 . A method for preparing a microfluidic device comprising:
 a) providing a photosensitive element comprising a solid layer of a photopolymerizable composition comprising a binder, a monomer, and a photo initiator;   b) imagewise exposing the photopolymerizable layer to actinic radiation through a mask, forming at least a cured portion and an uncured portion of the layer;   c) treating to remove the uncured portion from the layer and thereby form a precursor of the cured portion having an exterior surface and a relief pattern comprising at least one channel that is open to the exterior surface; and,   d) disposing a cover member above the exterior surface of the precursor to enclose the channel and form the microfluidic device.   
     
     
         2 . The method of  claim 1  further comprising:
 e) degassing the precursor of the microfluidic device of step d) by applying vacuum. 
 
     
     
         3 . The method of  claim 2  wherein step e) comprises placing the microfluidic device of step d) into an enclosure and applying the vacuum to seal the enclosure. 
     
     
         4 . The method of  claim 1  wherein the relief pattern comprises the at least one channel and at least one chamber in communication with the at least one channel, wherein the at least one channel has a depth from the exterior surface, and the at least one chamber has a depth from the exterior surface, further wherein the depth of the chamber can be the same or different than the depth of the channel. 
     
     
         5 . The method of  claim 4  wherein the depth of the chamber is greater than the depth of the channel. 
     
     
         6 . The method of  claim 4  further comprising prior to step d), applying a diagnostic reagent in the chamber. 
     
     
         7 . The method of  claim 4  wherein the relief surface further comprises at least one fill-enhancing duct that is in direct or indirect communication with the at least one chamber, wherein the fill-enhancing duct is not in direct communication to the least one channel. 
     
     
         8 . The method of  claim 7  wherein the at least one fill-enhancing duct is directly or indirectly in communication with one or more additional fill-enhancing ducts that are not directly in communication to the at least one channel. 
     
     
         9 . The method of  claim 1  wherein the at least one channel communicates with two or more chambers. 
     
     
         10 . The method of  claim 9  further comprising prior to step d), applying a different diagnostic reagent in each of the two or more chambers. 
     
     
         11 . The method of  claim 9  wherein the at least one channel has a depth from the exterior surface, a first chamber of the two or more chambers has a depth from the exterior surface, and a second chamber of the two or more chambers has a depth from the exterior surface, further wherein the depth of the first chamber can be the same or different from the depth of the channel and can be the same or different from the depth of the second chamber. 
     
     
         12 . The method of  claim 1  wherein the photopolymerizable layer is adjacent a support and has a thickness, and wherein prior to the treating step c), the method further comprising exposing the photosensitive element to actinic radiation through the support to form a floor of the photopolymerizable layer that is a cured layer having a thickness that is less than the thickness of the photopolymerizable layer. 
     
     
         13 . The method of  claim 1  wherein the photosensitive element further comprises a digital layer that is opaque to actinic radiation and sensitive to laser radiation, and is disposed on or adjacent the solid photopolymerizable layer, the method further comprising imagewise exposing the digital layer to laser radiation prior to step b) to form the mask on or adjacent the solid photopolymerizable layer. 
     
     
         14 . The method of  claim 1  wherein the photosensitive element includes a support adjacent the photopolymerizable layer and a top surface that is opposite the support, wherein the imagewise exposing step is selected from
 b1) contacting a phototool to the top surface of the photosensitive element, optionally drawing vacuum of the phototool to the photosensitive element and, exposing the photopolymerizable layer to the actinic radiation through the phototool as the mask; 
 b2) creating a digital mask as the mask by imagewise exposing a digital element to laser radiation, placing the digital mask adjacent the top surface of the element, optionally laminating the digital mask to the photosensitive element, and exposing the photopolymerizable layer to the actinic radiation through the digital mask; 
 b3) imagewise exposing a digital layer that is disposed on or adjacent to the photopolymerizable layer to laser radiation to selectively remove portions of the digital layer from the photosensitive element, and thereby form an in-situ mask as the mask, and exposing the photopolymerizable layer to the actinic radiation through the in-situ mask; 
 b4) imagewise exposing a digital layer disposed on an image element that is adjacent to the top surface of the photosensitive element to laser radiation to selectively transfer portions of the digital layer to the photosensitive element, and thereby form a digital mask as the mask disposed above the photopolymerizable layer, and exposing the photopolymerizable layer to the actinic radiation through the digital mask; or 
 b5) imagewise applying by ink-jetting an actinic radiation opaque material on or above the photopolymerizable layer to form an ink mask as the mask, and exposing the photopolymerizable layer with the actinic radiation through the ink mask. 
 
     
     
         15 . The method of  claim 14  wherein the laser radiation emits in the range 750 to 20,000 nm. 
     
     
         16 . The method of  claim 1  wherein the binder is an elastomeric binder selected from poly(styrene-butadiene-styrene) block copolymers, poly(styrene-isoprene-styrene) block copolymers, poly(styrene-isoprene-butadiene-styrene) block copolymers, or combinations thereof. 
     
     
         17 . The method of  claim 1  further comprising forming the cover member by overall exposing a second photosensitive element comprising a solid layer of a photopolymerizable composition comprising a binder, a monomer, and a photoinitiator to actinic radiation to form a cured polymeric layer. 
     
     
         18 . The method of  claim 17  wherein the binder for the second photosensitive element is selected from poly(styrene-butadiene-styrene) block copolymers, poly(styrene-isoprene-styrene) block copolymers, poly(styrene-isoprene-butadiene-styrene) block copolymers, or combinations thereof; and wherein the photopolymerizable composition of the second photosensitive element can be the same or different from the photopolymerizable composition of the photosensitive element of step a). 
     
     
         19 . The method of  claim 17  wherein for the disposing step d) the exterior surface of the precursor and/or a surface of the cover member that mates with the exterior surface of the precursor is sufficiently tacky to adhere the cover member and the precursor. 
     
     
         20 . The method of  claim 1  further comprising applying an adhesion promoting treatment to the exterior surface of the precursor and/or a surface of the cover member that will contact the exterior surface, prior to step d). 
     
     
         21 . The method of  claim 1  wherein prior to step d) further comprising forming the cover member by exposing to heat or actinic radiation a liquid layer of a polymerizable composition selected from polydimethylsiloxanes or perfluoropolyethers, to form a cured polymeric layer. 
     
     
         22 . The method of  claim 1  wherein the cover member is selected from a glass sheet; or a polymeric film that is selected from polydimethylsiloxanes, perfluoropolyethers, polystyrenes, polyethylenes, polypropylenes, polycarbonates, fluoropolymers, polyamides, polyesters; or combinations thereof. 
     
     
         23 . A photoimageable microfluidic device precursor element comprising:
 a solid layer of a photopolymerizable composition comprising a binder, a monomer, and a photoinitiator, wherein the solid layer is selectively imageable and removable to form at least one channel for transporting a fluid therein.   
     
     
         24 . The photoimageable microfluidic device precursor element of  claim 23  further comprising a digitally imageable element layer having a digital layer disposed above the solid photopolymerizable layer. 
     
     
         25 . The photoimageable microfluidic device precursor element of  claim 23  further comprising a digital layer disposed on or adjacent the solid photopolymerizable layer wherein the digital layer is opaque to actinic radiation and sensitive to infrared laser radiation. 
     
     
         26 . The photoimageable microfluidic device precursor element of  claim 23  further comprising a digital layer disposed on or adjacent the solid photopolymerizable layer wherein the digital layer comprises i) an infrared-absorbing material, ii) a radiation-opaque material, wherein i) and ii) can be the same or different; and, iii) an optional binder. 
     
     
         27 . The photoimageable microfluidic device precursor element of  claim 23  further comprising a mask having a pattern corresponds to selectively image the at least one channel. 
     
     
         28 . The photoimageable microfluidic device precursor element of  claim 27  wherein the mask further comprises a pattern to form one or more fill-enhancing ducts that are directly or indirectly in communication with at least one or more chambers but the one or more fill-enhancing ducts are not in communication with the at least one channel. 
     
     
         29 . The photoimageable microfluidic device precursor element of  claim 23  further comprising a support that is adjacent to the solid photopolymerizable layer and is a self-supporting film selected from polystyrenes, polyethylenes, polypropylenes, polycarbonates, fluoropolymers, polyamides, or polyesters. 
     
     
         30 . The photoimageable microfluidic device precursor element of  claim 23  wherein the binder is selected from natural polymers or synthetic polymers of conjugated diolefin hydrocarbons; block copolymers comprising a non-elastomeric block of vinyl polymer and an elastomeric block of a conjugated diene; nitrile elastomers; polybutylene elastomers; polyalkyleneoxides; elastomeric polymers and copolymers of acrylates and methacrylates; elastomeric polyurethanes; elastomeric polyesters; elastomeric polymers and copolymers of ethylene-propylene; elastomeric polymers of ethylene-propylene-diene; elastomeric copolymers of vinyl acetate and its partially hydrogenated derivatives; block copolymers comprising a non-elastomeric block of vinyl polymer and an elastomeric block of a conjugated diene that are chemically modified with fluoroalkyl groups, fluoroalkyl side chains, or with hydroxyl side groups; or combinations thereof. 
     
     
         31 . The photoimageable microfluidic device precursor element of  claim 23  wherein the binder is an elastomeric binder selected from poly(styrene-butadiene-styrene) block copolymers, poly(styrene-isoprene-styrene) block copolymers, poly(styrene-isoprene-butadiene-styrene) block copolymers, poly(styrene-ethylene butylene-styrene) block copolymers, poly(styrene-ethylene propylene-styrene) block copolymers, poly(styrene/butadiene/styrene) copolymers that are modified to have fluoroalkyl groups or fluoroalkyl side chains or side chains with hydroxyl groups, poly(styrene/isoprene/styrene) copolymers that are modified to have fluoroalkyl groups or fluoroalkyl side chains or side chains with hydroxyl groups, poly(styrene/isoprene-butadiene/styrene) copolymers that are modified to have fluoroalkyl groups or fluoroalkyl side chains or side chains with hydroxyl groups, or combinations thereof. 
     
     
         32 . A microfluidic device precursor comprising:
 a photocured layer of a photosensitive element comprising a support and a solid layer of a photopolymerizable composition comprising a binder, a monomer, and a photoinitiator adjacent the support, the photocured layer having an exterior surface opposite the support and is a channel-bearing layer comprising at least one channel for transport of a fluid, and optionally at least one chamber that communicates with at least one channel, wherein the at least one channel and the optional at least one chamber are open to the exterior surface.   
     
     
         33 . The microfluidic device precursor of  claim 32  wherein the photocured layer further comprises the at least one chamber. 
     
     
         34 . The microfluidic device precursor of  claim 32  wherein the binder is selected from poly(styrene-butadiene-styrene) block copolymers, poly(styrene-isoprene-styrene) block copolymers, poly(styrene-isoprene-butadiene-styrene) block copolymers, or combinations thereof. 
     
     
         35 . The microfluidic device precursor of  claim 33  wherein the at least one channel has a depth from the exterior surface, and the at least one chamber has a depth from the exterior surface, further wherein the depth of the chamber can be the same or different than the depth of the channel. 
     
     
         36 . The microfluidic device precursor of  claim 35  wherein the depth of the chamber is different from the depth of the channel. 
     
     
         37 . The microfluidic device precursor of  claim 32  wherein the photocured layer further comprises a pattern of one or more fill-enhancing ducts that are directly or indirectly in communication with one of the at least one chambers, but the fill-enhancing ducts are not in direct communication with the at least one channel. 
     
     
         38 . The microfluidic device precursor of  claim 32  further comprising a cover member disposed in contact with the exterior surface to enclose the at least one channel. 
     
     
         39 . The microfluidic device precursor of  claim 32  wherein the exterior surface of the photocured layer and/or a surface of the cover member that mates with the exterior surface is sufficiently tacky to adhere the cover member and photocured layer. 
     
     
         40 . The microfluidic device precursor of  claim 38  wherein the cover member is selected from
 a photocured layer of a second photosensitive element comprising a solid layer of a photopolymerizable composition comprising a binder, a monomer, and a photoinitiator; 
 a cured layer of a polymeric material selected from polydimethylsiloxanes or perfluoropolyethers; 
 glass sheet; 
 a self-supporting polymeric film selected from polystyrenes, polyethylenes, polypropylenes, polycarbonates, fluoropolymers, polyamides, or polyester; 
 or combinations thereof. 
 
     
     
         41 . The microfluidic device precursor of  claim 40  wherein the cover member is the photocured layer of the second photosensitive element, and wherein the cover member is tacky sufficient to adhere to the exterior surface of the photocured layer. 
     
     
         42 . The microfluidic device precursor of  claim 40  wherein the cover member is selected from the photocured layer of the second photosensitive element or the cured layer of polymeric material, and wherein a surface of the cover member that mates with the photocured layer and/or the exterior surface of the photocured layer has an adhesion promoting surface. 
     
     
         43 . The microfluidic device precursor of  claim 40  wherein the cover member is selected from the photocured layer of the second photosensitive element or the cured layer of polymeric material. 
     
     
         44 . A de-gas driven microfluidic device comprising:
 a photocured layer of a first photosensitive element comprising a solid layer of photopolymerizable composition comprising a binder, a monomer, and a photoinitiator, the photocured layer having an exterior surface and is a channel-bearing layer comprising at least one channel for transport of a fluid, and optionally at least one chamber that communicates with at least one channel, wherein the at least one channel and the optional at least one chamber are open to the exterior surface;   optionally, a diagnostic reagent disposed in the at least one chamber; and,   a cover member disposed in contact with the exterior surface enclosing the at least one channel, and the at least one chamber if present;   wherein the photocured layer is degassed.   
     
     
         45 . The de-gas driven microfluidic device of  claim 44  wherein the device is held in a vacuum such that, when subjected to atmospheric air, the fluid is driven to flow in the at least one channel. 
     
     
         46 . The de-gas driven microfluidic device of  claim 44  wherein the first photosensitive element further comprises a support adjacent to the solid layer of the photopolymerizable composition and opposite the exterior surface. 
     
     
         47 . The de-gas driven microfluidic device of  claim 44  wherein the cover member is selected from
 a photocured layer of a second photosensitive element comprising a solid layer of a photopolymerizable composition comprising a binder, a monomer, and a photoinitiator, wherein the photopolymerizable composition of the second photosensitive element can be the same or different than the photopolymerizable composition of the first photosensitive element; 
 a cured layer of a polymeric material selected from polydimethylsiloxanes or perfluoropolyethers; 
 glass sheet; 
 a self-supporting polymeric film selected from polystyrenes, polyethylenes, polypropylenes, polycarbonates, fluoropolymers, polyamides, or polyester; 
 or combinations thereof. 
 
     
     
         48 . The de-gas driven microfluidic device of  claim 44  wherein the exterior surface of the photocured layer or a surface of the cover member that mates with the photocured layer is sufficiently tacky to adhere the cover member and the photocured layer. 
     
     
         49 . The de-gas driven microfluidic device of  claim 44  wherein the at least one channel has a depth from the exterior surface, and the at least one chamber is present and has a depth from the exterior surface, further wherein the depth of the chamber can be the same or different than the depth of the channel. 
     
     
         50 . The de-gas driven microfluidic device of  claim 49  wherein the depth of the chamber is different from the depth of the channel.